Dogs have been selectively bred for thousands of years. Initially the selections would have centred on domestication and useful qualities such as hunting ability. Later dogs were also selected to give attractive and distinctive forms resulting in a vast variety of types. The point at which a new variety becomes a breed can be difficult to decide. National kennel clubs often differ in their recognition of breeds and rare breeds may not be recognised outside their home country.

Many traditional breeds recognised by the main registries are said to be "purebred". Only individuals whose parentage consists only of other purebred examples of the breed are regarded as part of that breed. This concept has caused controversy both because of the difficulty of regulation and because of the possible genetic consequences of a limited population.

The list below uses a wide interpretation of "breed". Breeds listed here may be traditional breeds with long histories as registered breeds, rare breeds with their own registries, or new breeds that may still be under development. Please see individual articles for more information.